Human and rats are born with insufficient levels of carnitine for normal fatty acid oxidation during fasting. This deficiency is usually rapidly alleviated by dietary carnitine from milk or formulas. However with the increasing demand for producing formulas with defined constituents, it is essential to determine if carnitine supplementation is required during early infancy. This project by determining the age of the development of the carnitine biosynthetic pathway will yield the ages in which infant formulas have a carnitine requirement. In addition, knowledge will be obtained of the age of onset of each of the enzymes of the carnitine biosynthetic pathway. Human carnitine deficiency, a disease characterized by fatty infiltration of the affected tissues, is a seriously debilitating, often fatal disease. A better understanding of the cellular and molecular mechanisms of the regulation of carnitine levels will provide a basis for better treatment of these patients. This study involves the determination of the source of carnitine which causes an increase in hepatic carnitine levels following an increase in the glucagon: insulin ratio. Kidney has a unique ability of acccumulating trimethyllysine. The relationship of this process to the transport of carnitine will be investigated. The regulation of the accumulation of trimethyllysine in the kidney may be a key to the regulation of carnitine biosynthesis.